In U.S. Pat. No. 3,646,931 (Phelps et al.) there is described a "portable battery-powered instrument for visualizing the peripheral pulse waveform and pulse rate", which instrument possesses many advantages over prior devices designed to perform the same or similar functions. For example, a very important advantage of the instrument described in this patent is the relatively small size thereof which enables the instrument to be used with neonates (newborns). Further improvements on prior art devices in this general field are disclosed in U.S. Pat. No. 3,734,086 (Phelps, Sr.) which relates to "equipment for measuring and displaying the time lapse between a given heartbeat and the corresponding arterial pulse". These patents both disclose work of the inventor in the present application and the disclosures of both patents are hereby incorporated by reference.
The present invention represents a substantial improvement over the devices referred to above as well as other prior art heart monitoring devices and rather than discuss the problems and shortcomings of the prior art in more detail, the advantages of the present invention will be considered in relation to the prior art in general and U.S. Pat. Nos. 3,646,931 and 3,734,086, in particular, although reference may be made to these latter patents for a further discussion of the general background of this invention and the prior art.